With gradual exhaustion of fossil fuel and increasingly serious environmental pollution, it is imperative to seek for a nonpolluting, renewable energy. Making the best of solar energy is of great economic and strategic significance to achieve sustainable development in low-carbon model. Polycrystalline silicon is the main raw material for fabricating solar photovoltaic cells. Fracturing polycrystalline silicon, as the last production procedure for a polycrystalline silicon production enterprise, is directly associated with the quality of polycrystalline silicon and enterprise benefit.
Recently, in most polycrystalline silicon production enterprises, polycrystalline silicon is fractured by using mechanically fracturing methods which can be classified into manually fracturing methods and automatically fracturing method. In a manually fracturing method, polycrystalline silicon is smashed with a hammer (or other rigid tools) and then screened and packaged. In an automatically fracturing method, polycrystalline silicon is crushed by a mechanical fracturing apparatus (e.g. jaw crusher, impact crusher, and the like). In the above two methods, polycrystalline silicon is fractured due to the pressure generated by a mechanical collision between a tool for fracturing and the polycrystalline silicon to be fractured, and both methods suffer from the disadvantages as below.
1. The mechanical collision between the tool for fracturing and the polycrystalline silicon to be fractured inevitably causes metal contamination, particularly iron contamination which significantly reduces the lifetime of minority carrier of polycrystalline silicon.
2. In the mechanical fracturing process, it is inevitable to generate enormous debris and micro powder, thus lowering yield and affecting the quality of polycrystalline silicon and enterprise benefit badly.
3. The debris and micro powder generated in the fracturing process may pollute the environment and are detrimental to employee's health, besides, tiny dust is inflammable and explosive in the air, which constitutes a hidden danger.
In addition, the traditional methods for fracturing polycrystalline silicon can hardly achieve effective control over the sizes of fractured polycrystalline silicon. However, the sizes of fractured polycrystalline silicon are of great importance for a polycrystalline silicon production enterprise, and the reasons therefor are explained as follows. For polycrystalline silicon before being fractured, it typically is a cylindrical polycrystalline silicon rod with a diameter of 80˜200 mm, a length of 200˜2800 mm and a smooth surface or a surface with nodules thereon, or a polycrystalline silicon lump with a linear dimension of 80˜300 mm. However, fractured polycrystalline silicon has irregular shapes and randomly distributed sizes. According to the relevant national standard, the distribution range of sizes of fractured polycrystalline silicon is specified as follows: polycrystalline silicon with a linear dimension of 6˜25 mm takes up 15% of total weight at most; polycrystalline silicon with a linear dimension of 25˜50 mm takes up 15%˜35% of total weight; and polycrystalline silicon with a linear dimension of 50˜100 mm takes up 65% of total weight at least. In other words, a linear dimension of 50˜100 mm is the optimum size for the fractured polycrystalline silicon. As it is inevitable to generate some small-size silicon lumps in the process of fracturing polycrystalline silicon, only a small amount of polycrystalline silicon with a linear dimension of 6˜25 mm is allowed.